I primarily use 1DX bodies but I picked up a 5DS R. It is an interesting camera with the higher resolution but it "handles" a little differently because of that and one thing I noticed is motion blur becomes more evident with the higher resolution. You may find you need to use a higher shutter speed than you are used to for a given lens. It isn't a huge deal but it is something of which to be aware before you purchase.
The files from it are also very large. 55 to 65 MB RAW files are typical but it isn't unusual to see RAW files over 90 MB so be prepared in terms of storage and processing speed. Because of the huge file size, the burst speed and buffer depth is also reduced.
The prices are low because these cameras are basically out of production, nothing wrong with that because they still do an excellent job.
I was actually surprised how often I use this camera. It definitely doesn't have the low light performance of my 1DX bodies but I was surprised at its noise performance in the 3200 to 6400 ISO range and that improves further if you downsample to a more typical pixel count when you convert to JPG.
The 5DS and the R variant (slightly better potential resolution at the possible expense of artifacts that can be addressed in post due to the different lowpass filter setup) are basically built on the 5 D III architecture so they are a bit behind some of the function of the 5D 4 but I consider them a true bargain for general use, landscape, portrait use, etc.
Rodger
EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video
